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(NoModeL) I A 2 SheetsSheet 1. J. J. OARTY.

TELEPHONE CIRCUIT AND APPARATUS.

No. 449,106. Patented Mar. 31, 1891.

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(NoModeL) 2 Sheets-Sheet 2.

J. J. GARTY. TELEPHONE 013mm AND APPARATUS.

No. 449,106. Patented Mar. 31, 1891.:

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'NITED- STATES PATENT HN J. OARTY, OF NEW' YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS,

TO THE AMERICAN BELL TELEPHONE COMPANY, OF BOSTON, MASSA- OHUSETTS.

TELEPHONE CIRCUIT AND APPARATUS.

SPECIFICATION forming part (if Letters Patent No. 449,106, dated March 31, 1891.

Application filed August 16, 1890- Serial No. 362,152. (No model.)

To all whom it may concern;

Be it known that I, JOHN J. OARTY,'residing at New York, in the county of New York and State of New York, have invented oer \{fain Improvements in Telephone Circuits and fl'pparatus, of which the following is a speci- *fication.

In the practice of telephonic communication it is often desirable to construct circuits having a number of stations. Particularly is this convenient in the case of private telephone-lines-such, for example, as are extensively used to connect telephonically the different offices and agencies of a railway in a large city or the headquarters of a manu- Eacturing concern with a number of factories. To avoid disturbances consequent upon the employment of the earth as a return, and also to avoid induction due to foreign circuits, me- Callie circuits of which the earth forms no part are frequently constructed, the circuit being constituted of an outgoing and a return wire extended in parallelism and closely adjacent to each other. Prior to my invention it was customary to connect the call-bell magnets at the several stations in series in the main-line circuit, together with a normally-shunted call-sending generator, and at each station to provide a switch usually actuated automatically by the removal and replacement of the receiving-telephone, which in one positionthat of rest-maintained the continuity of the main circuit through the said call-bell magnets and kept the circuit of the local transmitter-battery open, but which on the removal of the receiver from its support disconnected or short-circuited the said bell-magnet and generator from the line, introd need in place thereof the telephonic transmitting and receiving instruments, and closed the local-battery circuit of the former.

It is evident, however, that, though at any two stations on a multiple-station line the switches may have been operated, and the Fell-magnets consequently thereby removed from the circuit, the telephones having been substituted therefor, no such action takes ace at the remaining stations of such line. ence the telephonic or voice currentsneccssarily have to traverse all of the said magnet-helices, and of course are very much weakened in virtue, not only of the actual resistance of said magnets,but also and mainly in virtue of the counter electro-motive forces or inductive resistances developed in each of them, which, in fact, are so active and energet-ic as to render conversation frequently impracticable; yet it is absolutely essential that the said bell-magnets must be connected with the circuit, as otherwise the several sta- 6o tions cannot signal each other. Furthermore,

it has been found impracticable to obtain a perfectinductive balance in a metallic telephone-circuit when the bell-magnets and telephones are connected in series, and, since without a balance of the two sides of the circuit between any two telephones it is impossible to have an undisturbed line, it follows that the result of the serial method of connection in a multiple-station circuit is precisely that which the use of a metallic circuit is designed to obviateviz., an inductive disturbance which manifests itself in such telephones as are at any time in use, and which is always annoying, and sometimes so intense as to prevent intelligible communication. It is evident that if the series mode of connection both for call bell magnets and telephones could be totally abandoned and the entire apparatus at all stations connected in multi- 8o ple or bridging circuit between the two mains, after the manner of the simplest expression of an incandescent lighting system, these practical disadvantages would be eliminated; but

it is also evidentthat the conditions are totally difierent, for in a telephone-circuit each station is at one moment a generating and at another a utilizing station, and," unless some means be provided to prevent, the currents developed at any station when acting in the. former capacity are likely, irrespective of their character, to be short-circuited by the nearest bridging-station on either side and to utterly fail of affecting the station with which correspondence is desired, which. of course at any time may be the most distant one. Not only so, but the fact that two quite diverse-electrical applications are to be put in'practice by the same stations-t. e.,signaling and the transmission of speechand that I00 both of these applications are to be directed at any time from any station to any other station likewise militates against the satisfactory employment of a simple parallel arrangement and renders material additional invention imperative.

The object of my present invention, broadly stated, is in a multiple-station circuit to arrange the apparatus in parallel circuit or multi ple are, preferably on a metallic circuit, and to be able from any one station to satisfactorily signal all of the other stations, and also to enable the telephonic transmission and reproduction of conversation between any desired two of the said stations to be successfully effected. I have found that by a peculiar construction of the telephonic and signaling appliances at the several stations and by a peculiar arrangement of the same with regard to each other and also with regard to the main circuit these functions can efficiently be perform ed, the conversation reproduced at any station receiving being especially satisfactory.

To this end my invention comprises the employment of bell-magnets having a high coeificient of self-induction,the discontinuance of the ordinary practice of includingthe callsending generator and the call-bell magnets serially in the same circuit when calling, the connection of the said appliances in different and parallel bridge, cross-wire, or derived circuits of the main line, the bell-magnet-bridge being normally and permanently closed or continuous at all stations, and the generatorbridge circuit being normally open or discontinuous, but adapted to be closed while sending a call, the connection of the telephones in a third bridge-circuit at each station, this also beingopenwhenthetelephoneisnotactuallyin use,but closed in multiple arc with its own bellmagnet, and of course with the bell-magnets of other stations, when in use, and other combinations of the above features to be more specifically hereinafter pointed out in the several claims at the end of this specification. By adopting these improvements and combining them as shown in the drawings and described herein I am enabled to provide signaling and telephonic systems which are selfregulating and which have proved in actual practice to be perfectly efiicient and satisfactory.

In the drawings, Figure 1 is a diagram of a telephone-circuit having a number of stations and embodying my invention. Fig. 2 is a diagram of a station apparatus and its electrical connections complete; and Fig. 3 is an elevation of the bell-magnets I prefer, indicatin g the actual size of the same,and showing thereby one mode of raising the self-induction of said magnet to the required height.

In the diagram the telephone-circuit as a whole is represented by the letter L, and its two lin e-wires, respectively, are designated as land P. It is a diagram of a line which I have actually constructed and have put in operation,and has eleven stations, designated by the figures 2 to 12. At station 9 the apparatus and electrical connections are indicated, and in Fig. 2 the same connections are more completely illustrated, the different elements of the construction brought together in a concrete appliance being more clearly shown.

Inasmuch as the apparatus and mode of connection are the same at all stations,it is necessary to show and describe one only. I have, however,indicated them symbolically at several of the others. It will be seen that at each station the apparatus is connected with the two wires of the main line, a wire 13 extending inward from line-wire l, and a wire 14 from line-wire 1*. Should any telephone-station be nearer to one of these loops than itis to the main line, a second loop may be connected with the two wires of the first, as shown at stations 5 and 6, where a branch 13 extends from junction with the wire 13 to station 6, returning by wire 14 to a junction with wire 14.

As shown at station 9, B indicates the callbell magnets included permanently in a bridge or cross-wire extending across the loop between station wires 13 and 14, although if L were an earth-completed circuit the said magnets would be included in a permanentlyclosed earth branch. When the call-bells are connected at a number of stations on a single line in multiple are, it is of course required that call-signals transmitted from any station shall ring the bells at all of the stations; that having signaled and attracted the attention of any given station conversation can be readily exchanged therewith, and that the loudness of the reproduced speech must not be impaired or perceptibly diminished by the permanent connections between the two main wires Z and 1 involved by the presence of the bell-magnets connected, as described, at the unemployed stations. This can best be accomplished by providing call-bell electromagnets which have a high coeflicient of selfinduction. To construct bell-magnets fulfilling this requirement, 1 lengthen out the iron cores,which are yoked together by an iron heelpiece, as usual, and wind the electro-magnet complete with No.33 silk-covered copper wire up to a resistance of one thousand ohms-that is, of course, five hundred ohms on each spool. Such a magnet is shown in Fig. 3. Each of the two spools of the electro-magnet B in-. closes an iron core w, the two cores being united at the rear by an iron heel-piece II, which may also serve as a portion of the frame of the ringer. fixed in the frame F, to which also a permanent magnet 19 is secured in a manner well understood, in such a way as to polarize the two cores w with one polarity, and the centrally-pivoted armature R, which carries the bell-hammer rod 01, and which is pivoted at q in lucs projecting from the front bar F of the frame F, inductively, with opposite polarity. The hammer n vibrates between bells The magnets L are B to give the signal, as usual. By lengthening the legs of the electro-magnet and by winding it with the size and amountof wire described it is evident that I am enabled to utilize a great number of convolutions, and

the magnet, together with its armature R,

forms a system adapted to develop a very high self-induction.

It has been demonstrated by experience when ringer-magnets constructed as above are used that the ordinary mode of connecting them serially in the same circuit with the generator-coils is impracticable, for the reason that when so arranged the resistance of the magnet-helices virtually becomes a portion of the internal resistance of the generator, and when the internal resistance of the generator-circuit is thus increased the generator itself is not self-regulating, and it is 2 1 not possible to satisfactorily ring or to receive calls from other stations. Having therefore,

as described, increased the resistance and self-induction of the several bell-magnets, I

connect the said magnets at all stations in a 2 permanent bridge of the main line, as in the diagram of station 9, where the bridge leads from the point it on wire 13 by the wires 24 and and through the said bell-magnets B to the pointt' on wire 14. No other appliance 3 is included in this permanent bridge or crosswire, and the automatic telephone-switch s has no control over the said bell branch, which is unadjustable. No other 'path through the station for the circuit is normally closed, so

3 that the full force of any ringing-current entering the said station when the said station is not itself using the line necessarily traverses the bell-magnet helices and produces energetically the incoming signal.

The outgoing signals are transmitted by a hand magneto-generator G, as usual. This is included in a second bridge or cross-wire, which, however, is normally open, and which is only closed while the station is in the act t5 of transmitting a call. It is brought into action by operating the circuit-closer 70, which,

as shown, is a manually-operated key, but which may of course be an automatically-op- {rated circuit-controller actuated by the op- ;c aration of turning the crank-handle of the generator when a signal is being sent in a manner well understood in the art. When {he generator-bridge is closed in this way,

it forms a second bridge or cross connection "5 between the wires 13 and 14, and hence between the" main wires Z and Z in parallel circuit with the permanently-closed bridge- (jrcuit of its own bell, and, in fact, in parallel circuit,also, with the bridge-circuits of the ells at all of the other stations. Although ardinarily the tendency with such a mode of mnnection would be to short-circuit the ring- 'l gcurrents through the home bell, and pos- 351 y, also, through one or two of the nearest of sa e others, this tendency is practically obvied by the high self-induction and resistance the bell-magnets, which determines a correspondinglyhighcounterelectro-motive force in each, opposing the passage of the impressed ringing-current, and also aiding the said impressed ringing-current in distributing itself impartially between the remaining bell-magnets. It is also to be noted that though in virtue of this self-induction a comparatively small portion of the ringing-current passes through each bell-magnet, yet that such portion as does pass is enabled by means of the numerous windings of wire to exercise a very considerable magnetizing effect on the cores, and consequently to operate the said bells with great energy. I place the telephonic receiving and transmitting instruments also in a normally-open cross-wire or bridge between the two sides of the line. This is controlled by the automatic telephone-supporting switch 8. When the receiving-telephone is in place and the station at rest, the telephone-bridge circuit is open or broken at the upper contacts of said switch, and the local transmittercircuit is also open; but when by the removal of the telephone-receiver from its support the switch 5, turning on its pivot g, is allowed to spring upward the telephone-bridge of the main line and also the transmitter-battery circuit are both closed, and the telephones when being used are connected in multiple arc with the bell-magnets at their own and at other stations, and also with the corresponding telephones. Of course, if desired, a handoperated switch may be, whenever desired, substituted for the automatic switch s. These connections may be more easily comprehended by a study of Fig. 2, which, however, does not differ in any material point from station 9 of Fig. 1, and it will be seen by reference to either that each station comprises a normally and permanently closed bridge, including the bell-magnets, and two normallyopen bridges, including, respectively, the callsending. generator and the telephones, and each adapted when closed for use to form an additional bridge in the same station parallel to the bell-bridge.

In Fig. 2, 7t and t' may be regarded as the terminal connections of the station apparatus and as being united to the wires 13 and 14 of the main-line loop. The bell-magnets B are connected permanently between these terminal screws by way of wire 24, hinge II", magnets B, wire 25, and binge H. There is no other line of normal conduction between the station-terminals h and i.

The generator G is connected as an additional bridge between 7t and 2', and its circuit is normally open. It is closed while the signal is being sent, and when closed shunts and is shunted by the bell-magnets B. Its line of conduction is traceable from h by way of wire 26, point 6, key 7r, anvil f, generator G, wire 16, hinge H, and wire 25 to post 2'. It is closed by pressing the key or by some equivalent manual or automatic operation while the crank 'r of the generator is being revolved, and the signaling-currents are then sent to IIO line and actuate the bells at all of the stations simultaneously.

The telephones, as already stated, are in a third bridge, which also is normally open. In the drawings it is shown as being closed for operation by the removal of the receiver t from the hook of the switch and the consequent position of the said switch. The telephones are therefore ready for use, and their line of conduction from h to t' is as follows: from the post h by wire 26, point 6, wire 17, binding-screw m, receiver 25, screw m wire 22, screw m, the secondary helix T6 of the induction-coil I, screw on, wire 21, switch-bar 8, contacts 5 and c, and wire 27 to post 2'. The telephones therefore are thus included in a third bridge, which when closed shunts or is in multiple arc with the bell-magnets. Upon the removal of the receiver from the hook or yoke of said switch, the switch-bar, rocking upon its bearing g, brings its projecting piece 3 into contact with the two springs c and a, closing its bridge-wire through the former and completing the circuit of the local transmitter-battery I) through the latter. The said local circuit passes in the usual Way from one pole of the battery I) by way of screw terminal m and wire 20 to switch-contact a, thence when the switch is in position to close the circuits to said switch-contacts s switch bar 3, wire 21, binding-screw m wire 23, primary helix 1* of the induction-coil I, wire 18, transmitter T, and by wire 19 to the other battery-pole.

Then the receiving-telephone is in place, the projecting piece .9 of the switch will break contact with the springs c and a, and will thus open the circuit and telephone-bridge. \Vere the bell-magnets in the permanent station-bridges of but ordinary character, the telephones transmitting at any station would practically be short-circuited; but mine, being constructed to develop a high coefficient of self-induction, form an eifectual bar to shortcircuiting and act efficiently as inductive as well as ordinary resistances.

The switch 8 has no other functions than those I have stated, and thus the station apparatus has an additional incidental advantage over forms in which the bell branch also is controlled by said switch, in that one contact is totally dispensed with.

In my apparatus there are but three separable contacts in the entire outfit-namely, the generator-contact between 7t and f, the telephonebridge-conductor contact to be made when the switch-bar relieved from the receiver flies upward, and the battery-contact made in the same way. Inasmuch as defects in electrical apparatus develop most frequently at such contacts, it is obviously advantageous to diminish the number of these; and

I claim-- 1. A multiplestation telephone-circuit, a

branch circuit uniting the two sides of telephone-circuit, and a generator of tricity for sending calls at each of said tions, adapted when operated to be conne between the two sides of said telephont cuit in multiple arc with the call-bell mag substantially as described.

2. The combination, substantially as] inbefore described, of a metallic telepl circuit extending between a number of phone-stations, a permanently-closed hi or cross conductor at each station, unitin, two main conductors and including the bell magnets of said station, anormally-l bridge or cross conductor also at each sta including the call -sending generator, means for closing the said generator-hr in multiple arc with the permanent bri connection of said. bell-magnets.

3. The combination, substantially as scribed herein, of a metallic telephom cuit extending between a number of sub tions, at permanently-closed bridge-connet therefor at each station, call-bell mag having a high coefficient of self-inductio eluded therein, a normally open or dis tinuous bridge or cross conductor also at station, including an electrical transmit instrument, and adapted when closed tor the two wires of said metallic circuit thr the said transmittinginstrument and in tiple arc with the permanent bridge, a circuit-closer arranged to close the said: mally-open cross-conductor in the act of munication.

4. A metallic telephone-circuit exten by both of its main conductors to a nu: of telephone-stations, a permanently c; or continuous bridge or cross conduct! each station, uniting the said main cond nt call-bell magnets at each station includi said cross-conductor, anormally-open br circuit at each station, adapted to unite closed the said main conductors in pat circuit with the said closed bell-magn et br a telephone included therein, and a 0i] closing switch therefor, substantially a scribed. 5. A metallic telephone-circuit extet by both of its main conductors to a Ill of stations, in combination with a pa nently'closed bridge-conductor uniting said main conductors, call-bell magnetso ing a high coefiicient of self-inductio cluded in said permanent bridge, a norn open telephone branch circuit adapted closed also to form a bridge uniting the two main conductors, whereby the telepl5 thereof are connected with said circu multiple are with said bell-magnets, a switch for closing the said normally-open phone branch, substantially as and fo purposes specified. lo

6. The combination of a metallic telepl circuit extending by both of its main ductors to a number of stations with a manently-closed bell-magnet branch u at its terminals with the two main conductors,

ductors to a number of stations, of a normallyopen call-generator-bridge circuit adapted when closed to unite the two main wires through said generator, a circuit-closer therefor, an independent discontinuous telephonebridge circuit adapted when closed to unite the said two main wires through the telephones, an independent and automatic circuit-closer for said telephone-bridge, and a permanently-closed bridge uniting the said two main wires and having in its circuit the call-bell magnets, the said magnets constituting a high inductive resistance in parallel circuit with the said generator or telephone bridges when the said bridges are brought into action, for the purposes specified.

8. Atelephone-station apparatus comprising a permanently-continuous conductor uniting the main-line terminals of said apparatus, an electro-magnetic call-instrument included in the circuit of said permanent conductor, two normally open or discontinuous branch circuits also extending between the said terminals and adapted when closed to form additionalconnectionsbetween themin parallelcircuit with the said permanent conductor, a callgenerator included in one and a telephone included in'the other of said normally-open branch circuits, means, as indicated, for closing the generator branch circuit, and other means for independently closing the telephone branch circuit, substantially as described, and for the purposes set forth.

9. The combination, in a metallic-circuit station apparatus, of a call-bellhaving its electromagnetineluded in circuit with a permanently closed or continuous conductor uniting the two line-terminals of said apparatus, a callgenerator for sending signals included in a normally open or discontinuous conductor or branch circuit also extended between the said terminals, a circuit-closer adapted to close the said generator branch in parallel circuit with the permanently-closed bell-magnet conductor, transmitting and receiving telephones included in an independent normally open or discontinuous conductor or branch circuit also extending between said terminals, and an automatic switch actuated by the removal of the receiving-telephone to close the said telephone branch circuit as a shunt or in parallel with the permanently-closed bell-magnet branch, substantially as described.

a normally-open 10. In a metallic-circuit station apparatus, the combination of a permanently closed or continuous conductor uniting the two lineterminals of said apparatus, a call-bell provided with electro-magnets having a high coefficient of self-induction included in said continuous conductor and adapted thereby to be connected in circuit between the two main wires of a metallic circuit and to form a bridge therefor, and two normally open or discontinuous branch circuits including, respectively, a call-generator and telephones, each being independently provided with a circuit-closer whereby it may be connected with the main line in multiple arc with the bell-magnets, substantially as described.

11. The combination, in a telephone-station apparatus for metallic multiple station circuits, of terminals adapted, respectively, to connect with the two conductors of the main metallic circuit and three branch circuits extending through the apparatus from one of the said terminals to the other, two of the said branch circuits being normally open and one permanently closed, with a magnetogenerator and a circuit-closer in one of the said open branch circuits, a telephone and an independent and automatic circuit-closer in the other open branch circuit, and call-bell electro-magnets in the. permanently-closed branch circuit, constituting therewith an electro-magnetic shunt for both generator and telephone branches when the said branches are closed, substantially as described.

12. The combination of a metallic multiplestation telephone-circuit. with an apparatus at each station of the said circuit containing branch circuit extending from terminal to terminal of the said apparatus, and telephones included therein and forming part thereof, means actuated by the removal of the telephone from its support for automatically closing the same and for thereupon forming a closed bridge including the telephones between the two main-line wires, an independent and alternative normally-discontinuous branch circuit, a magneto-electric call-generator included therein and forming part thereof, and anindependentcircuit-closer for connecting the said generator between the said two main-line wires, and a permanentlycontinuous branch circuit having a high coefficient of self-induction and forming normally the sole conductive path between the said terminals and constituting a permanent electro-magnetic shunt for the said generator and telephone branch circuit-s, respectively, when the said branch circuits are closed, substantially as herein described.

18. The combination of a metallic multiplestation telephone-circuit and at each station an apparatus including the following instrumentalities: a normally-open branch circuit extending between the said two wires of said metallic circuit, including telephones, and adapted when closed to form a bridge through said telephones between said wires, an independent and alternative normally open branch circuit also extended between the said two main wires, including signal-sending devices, and adapted when closed to form. abridge uniting said main wires through said signalsending devices, and a closed branch circuit having a high coefficient of self'induetion permanently uniting said main wires and forming normally the sole conductive path at said station between said main wires, and thereby constituting a permanent electro-magnetic shunt for the said telephones and call-sending appliances when their branch circuits, respectively, are closed for operation.

14. A telephone-circuit extending between and connecting a nu mber of stations, a ringermagnet of relatively high resistance, as specified, at each station included in a branch circuit uniting the two sides of said teleph one-circuit, a generator of electricity at each station for sending outgoing calls, adapted when operated to be connected in an independent branch circuit between the two sides of said telephone-circuit in multiple arc with its associated ringer-magnet, and atelephone at each station also adapted when in operation to be connected between the two sides of said telephone-circuit, substantially as described.

15. In a telephone-station, a combined telephone apparatus comprising, substantially as hereinbefore described, a call -bell magnet of relatively high resistance in a branch circuit uniting the terminals of said apparatus, an electrical generator for sending outgoing calls in a normally-discontinuous independent branch circuit extending between the same apparatus terminals in multiple are with its associated bell-magnet and adapted to be closed when the said generator'is operated, and a telephone normally disconnected, but adapted to be connected when in operation between the said terminals of said apparatus.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 4th day of August, A. D. 1890.

JOHN J. CAR'IY. \Vitncsses:

WV. E. REOKNAGEL, JOHN H. CAHILL. 

